This invention relates to an endoscope having a section which can be inserted into a channel and, in particular, into a bent channel.
An endoscope which can be used to observe the inner surface of a bent channel, such as a water supply pipe or gas pipe, is known. Such an endoscope is generally referred to as an industrial endoscope and is a very effective and efficient means for observing the inner surfaces of, for example, a complex machine or a narrow tube.
As is shown in FIGS. 1 and 2, straight tubes 1 and 2 are jointed by elbow 3, with abrupt step 4 being formed between the straight tubes and the elbow. When the distal end of endoscope 5 is to be inserted to permit observation of the inner surface of the curved section of elbow 3, angle section 6 of endoscope 5 is bent, by means of an external operation, at abrupt step 4, so as to prevent it from abutting thereagainst. In this way, the end face of distal end 5 of the endoscope is oriented inwardly away from abrupt step 4, after which the distal end of the endoscope is pushed further into the channel of the tube.
In this case, if abrupt step 4 at the location of the elbow is pronounced, the possibility is increased that angle section 6 of the endoscope will become jammed against step 4 upon being moved along the inner surface of elbow 3. If jamming occurs, attempts to force the insertion section further into the tube will most likely result in damage to the angle section. Therefore, the insertion section must be partially withdrawn each time an obstacle is encountered and attempts are made to guide it away from the obstacle, so as for it to be inserted further into the tube. This makes usual inspection of the interior of the tube a more time-consuming proper than is desirable. Moreover, after the distal end of endoscope 5 has successfully negotiated, for example, three or more curves or bends, it becomes less likely, from a structural point of view, that angle section 6 of the endoscope will then be able to continue to bend sufficiently to be able to negotiate further bends or curves. As a result, distal end 7 of the endoscope becomes jammed against an obstruction, at which point it is no longer possible to continue observation of the interior of the tube.
Thus, where a tube comprises three or more abrupt bends or curves, the conventional endoscope ceases to be an efficient means of observing the interior of such a tube.
Japanese Patent Disclosure (KOKAI) No. 59-143401 discloses an industrial endoscope which permits clear observation of the interior of a tube by washing away any foreign matter coated on the inner surface of an observation window.
In this type of endoscope, opposite to the observation window provided at the face end of a rigid portion of the endoscope an outlet for injecting a washing liquid is formed at a hood attached to the rigid section of the endoscope or a washing liquid injecting nozzle is formed such that it is opened at the end face of distal-side rigid section of the endoscope.
This endoscope can effectively be used to observe the interior of the tube which is readily liable to be deposited with a dirty or rusty substance. This type of endoscope, however, never has any angle section and, if it has, poses such a problem as set forth above.
Japanese Patent Disclosure (KOKAI) No. 56-158631 discloses an industrial endoscope having a graduation mark within a visual field which is obtained through an eyepiece section.
This endoscope can precisely determine the size, etc., of a defect, such as a damaged spot, or a rusty spot on the inner wall of the tube and is very useful to observe the interior of the tube.
In order for the dimensions of a given part or spot to be accurately measured by means of the graduation, it is necessary that a predetermined distance be maintained between the distal end rigid section and, in particular, an observation window and a spot to be measured. For the exact determination of that distance for measurement, an optically, fairly complex structure results. In this case, the aforementioned problems occur when the distal end of the endoscope is inserted into a complicatedly bent tube, to observe its inner surface.